Periodically-varying-frequency motor-generator set



May 27, 1924. 1,495,236

- J. L. ADAMS, JR

PERIODICALLY VARYING FREQUENCY MOTOR GENERATOR SET Filed Nov. 17 1919 2Sheets-Sheet 1 J 6! Urn.

7'0 FIELD JIMMIII ARMATURE GENERATOR FIELD WITNESS Q INVENTOR v JamesL-A7dams./?

ATTORNEYS May 27, 1924.

J. L. ADAMS, JR

PERIODICALLY VARYING FREQUENCY MOTOR GENERATOR SET Filed Nov. 17. 1919 2Sheets-Sheet 2 James L Ada/wk [I] H g Y ATTORNEY Patented May 27, 1924.

UNITED STATES 1,495,236 PATENT OFFICE.-

J'AMES L. ADAMS, JR., OF MILWATIKEE, WISCONSIN, ASSIGNOR TO A. SMITHCOR,- PORATION, OF MILWAUKEE, WISCONSIN, A CORPORATION OF NEW YORK.

PERIODICALIIZY-VARYING-FREQ'l' EN'CY MOTOR-GENERATOR SET.

Application filed November 17, 1919. Serial No. 338,464.

To all whom it may concern:

Be it known that I, JAMES L. ADAMS, Jr., a'citizen of the United States,and residing in the city of Milwaukee, county of Mil- Waukee, and Stateof Wisconsin, have invented certain new and useful Improvements inPeriodically-Varying-Frequency Motor-Generator Sets; and I do declarethat the following is a full, clear, and exact description thereof, suchas will enable persons skilled inthe art to which the invention pertainsto make and use the same, reference being had to the drawings heretoattached and forming part of my specification for disclosure as to thedetails of construction and explanation of the mode of operation.

The invention relates to means for generating alternating electriccurrents of pcriodically varying frequencies. It has particularreference to motor-generators which are used to siipply electricalenergy to -motors driving machines or tools Whiclrmust be operatedintermittingly and alternately 2 in order to accomplish the purposes forwhich such machines or. tools are employed.

In application Serial No. 212,934, filed- January 21, 1918, by R.Stanley Smith, on which Patent No. 1,397,020, was granted November 15,1921, to which reference may be had, there is disclosed an assemblage,the several machines of which by their connected and related movementsperform in regular sequence the series of operations involved in theconversion of sheet metal plates or blanks into a completed andunit-zltry frame for an automobile or other vehic e.

The assemblage referred to'comprises machines which have for theirdependent and related functions, among others, the punching of blanksfrom metal sheets or plates to form the side and end and'cross bars ofan automobile frame, piercing such blanks at predetermined places forthe accommodation of the rivets employed to unite in one structure theseveral parts of the frame, shaping the blanks by flanging or offsettingso'that the side and end and cross bars will have the necessary degreeof rigidity, attaching brackets and gussets, machining or milling theseveral parts as required, assembling and clamping in correct relationthe elements of the frame, inserting rivets, and riveting the assembledparts together while alternatingperiods of rest will be of equal orsubstantially equal duration, but such pe riods may be varied each withrelation to the other, according to the particular exigencies which mayarise from time to time in differing constructions of work. Theassemblage is also provided with conveyor devices the purpose of whichis to convey. or transfer the work from machine to machine in regularprogression while the machines are at rest, the conveyor devices beingatrest in the intervals between conveying movements and during theinstants that the machines are performing their work operations.

My present invention has been especially constructed for the purpose ofeffecting the intermitting and alternating movements of the machines andconveyor devices above mentioned and disclosed in the patenthereinbefore referred to.

Such present invention has for its object the provision of a simple andefficient construction by means of which a plurality of alternatingelectric currents of periodically varying frequency can be generated. Ingenerating such currents the periodically re-. curring frequency maximaof the several currents occur at different instants in any given periodor time cycle, so that the maximum of frequency for the first'currentwill occur at a different instant than that of the second current, andso on, through the whole series of currents, if more than two beemployedf By this means,-I am enabled to produce currents to drive aplurality of groups of electric motors in such a way that while onegroup of motors is functioning, another group of motors will be standingstill, and vice versa. The groups of motors operate alternately,periodically and intermittingly, in recurrent time cycles each ofpredetermined time length. But it will be understood that the motors ofeach of the separate groups are operated insynchroi nism, although theseveral groups are oper- I of worlemovement and periods of conveyormovement, each alternating with periods of rest.

I prefer to use induction motors with distributed windings on bothelements, such as the wound-rotor type induction motor of commerce, andto supply alternating current of approximately constant frequency to thefirst element of the motor, which may be the rotor, and current ofvarying frequency to the second element, which may be the stator, asdisclosedin application Serial No. 315,- 189, filed August 4, 1919, byR. Stanley Smith and me as joint inventors. The current of constantfrequency which is supplied to all of the motors of the several groupsmay be generated in a common source, but

' the currents of varying frequency which are supplied to the motors inthe different groups are each generated in an independent source, as inthe application hereinbefore last referred to. y

The novel features of my present invention will be pointed out in theclaims appended to this specification.

In the drawings which accompany this I 1 specification,

Figure 1 is a view, partly in section,il1u stra-ting diagrammatically a"general construction embodying the invention, which latter willhereinafter be described in detail.

Fig. 2, illustrates a time-frequency chart, and is designed to show therelation, at suc-' 'cessive time instants in the recurring time cyclesor work periods, between the periodically varying frequency alternatlngcurrents, and a third current which may be one of approximately constantfrequency.

Referring to the drawings, the numeral 1, Fig. 1, indicates a doublerotation synchronous motor, and 2 and 3 indicate alternating currentgenerators. which latter are con I nected to and driven directly by therespective rotating elements of the motor 1, by the shafts 4 and 5.

The shafts 4 and 5 are connected through the speed reducing pinions 6,7, 8, 9, ltland 11, gears 12, 13. 13, 14, 15 and 16, the shafts 20 and21, and irregular or noncircular gears 17, 18 and 19, the purpose beingto transfer power from one end of the motor-generator set to the other.The shafts 4 and 5. above referred to extend in the same plane withtheir adjacent ends abutting, or substantially so. These shafts areconnected with each other, by means of trains of speed-reducing andaccelerating ed on short shafts which are held or journalled in theframe, as the case may be, and are connected-at their hubs with pinions7 and 10, meshing with gears 13 and 15. the latter being likewisemounted upon short shafts having a bearing in the frame of theapparatus. The gears 13 and 15 carry pinions 8 and 11, which latterengage gears 13 and 15, mounted upon shafts 20 and 21, journallcd inbearings which latter may depend from the frame. The shafts 20 and 21are not aligned axially as are the shafts 4 and 5, previously referredto, but are arranged in parallel planes so that gears 17 and 19, mountedupon the ends of the said shafts may transmit the motion from one shaftto the other through the medium of the said gears and theinterconnecting gear 18, the purpose of this arrangement being totransfer power from one end to the other as stated before. lVhile in theconstruction illustrated, only as an example, I have shown the pinionsand gears and irregular gears in the number and arrangement indicated,it is obvious that a lesser number of such pinions and gears may be usedto effect the purposes of my invention. The separate shafts 20 and 21are shown as connected by the irregular or non-circular gears 17, 18 and19, but only two of such gears may be neces sary in some cases.

ith a View to overcoming or greatly reducing the stresses required totransfer power from one end of the motor-generator set to the otherthrough the gearing described,I supplementthe gears by two varying speeddirect current machines, which may be shunt wound and which functionalternately as motors and as generators. These direct current shuntwound machines are indicated by the numerals 22 and 23,"in Flg. 1, andtheir rotors are mounted upon will permit of the operation of the entireI set for a few minutes, as may be necessary during an emergency whichmay arise from the interruption of the supply current which drives. themain double rotation motor of the set. i At the left of Fig. 1, I haveindicated by the numeral 32, the alternating current generator, whichsupplies a current of constant frequency through the power line 26, toone element of the double rotation synchronous motor 1. The otherelement of the motor 1, is supplied with direct current through line 27,from the battery 24.

At 30 and 31, I have illustrated conventionally two groups of motors,eachgroup of which may embrace any desired number of motors wired inparallel, if a plurality of motors be employed in each group. The

generators 2 and 3, through connections 28v and 29, supply alternatingcurrents of varyfrequency to the first elements of the respective motorsor groups of motors,-'30 and 31. The second elements of the said motorsor groups of motors are connected to the line 2G, said connectionssupplying currents of constant frequency to the; elements mentioned.

The speeds of the main motor generator set 1, are held within the rangeof a 1:3 variation from maximum to minimum by means of the gearing 6 to19, but the two direct current machines 22 and 23, are wound for a 4:1or a 3} 1 speed variation, the examples given in this last connectionbeing merely typical and not necessarily invariable. Under theseconditions, it will be evident that with full field strength on thedirect current machines 22 and 23, they can be made to run not only atthe lowest speeds required by the motor generator set 1, but can be madeto act as direct current enerators at these speeds, while at the igherspeeds they can in turn be made to function as direct current motors, iftheir fields are weakened to the opposite limit.

This strengthening of the field of the machine which is at a givenmoment operating at the lowest speeds, and weakening of the field of thedirect current machine which at the same moment is operating at thehighest speeds, is accomplished automatically. The devices which I usefor efi'ecting the result described are-constituted of a rheostat' 35,which is connected to the shunt field circuit 36, of the direct currentmachines 22 and 23. Upon one end of the shaft 3 1 of thegear 18, aneccentric or crank pin is mounted, which latter part operates a link 33,connected with the rheostat 35, so as to operate the latter. Theeccentric or crank pin may be mounted upon any convenient low speedshaft, instead of the shaft 34, as shown, and more than one rheostat 35,may be used, if

desired.

' of both stator and rotor are in the same direction about their shaftsas axes, and under these conditions the instantaneous speeds, inrevolutions per second, will be given by the difference in frequenciesin the two elements of each motor, divided by its number of pairs ofpoles. Thus, the respective speeds for the two groups of motors, willvary from instant to instant in accordance with the vertical distancebetween curves 28 and 29 and the common base line 26, in Fig. 2, whichdistances give respec tively the instantaneous difference in frequenciesbetween the lines orcircuits 28 and 26, and 29 and 26-. It will be notedthat at I points 37 or 38, or at any "other similarly situated points inthe succeeding work periods, the motor speed will be zero.

From what has been hereinbefore stated respecting the arrangement, itwill be evident that if the double rotation motor 1 is of the selfstarting type, and is thrown onto line 26, or if a small amount ofdirect current is fed through suitable starting rheostats to the motors22 and 23, the motor 1 willbe brought up to synchronous speed,

'which itwill then retain, and the two gen erators 2 and 3, togetherwith the two direct current machines 22 and 23, will subsequently riseand fall periodically in speed. This action willbe determined primarilyby the particular instantaneous positions of the irregular gears,whatever may be the number of the latter, with the link 33 moving backand forth so as to out in and out the resistance in the shunt fields ofthe direct current machines 22 and 23, in such exact timing as to causethem to endeavor to very slightly lead the speed changes in the maingear set, and consequently tend to practically relieve the latter of theload.

- The torques exerted by both elements of the double rotation maindriving motor 1,

, are exactly equal at any given instant, irrespective of the exactspeeds at which these two elements are operating at the moment.Therefore, at any given instant and for a given torque, the powerdeveloped by each element will vary in proportion to its speed ofrotation. The two elements of the main driving motor 'will never developexactly equalpowers, except when they are bot running at the samespeeds. 1

Asa consequence offthis condition. it is found in practice tobifnecessary to transfer power alternately from one end of the motorgenerator set to the other. This result I accomplish by varying in aproper manner the resistances in the shunt field c rcuits of the twodirect current machines 22 and 23, so that such machines will run at therequired speeds at all given points on each recurrent work cycle. Thesaid di- I rect current machines not only will work as described, but-.will also work as motor and generator, respectively, or vice versa, at

such points as may require material transfers of power from one end ofthe set to. the other, in order to equalize the torques developed by themain driving motor 1 in its have described as an, example, and in whichthe maximum and minimum speeds of the generators 2 and 3 have a ratio of3: 1.

The percentage of time of each work cycle or operating period,throughout which the generators2 and 3 are operating at their respectivemaximum and minimum speeds, will be dependent upon the particular shapeof the irregular gears, 17, 18 and 19, for instance, which may be usedat the time. As an example, I have shown an arrangement of gears whichwill permit of the operation of the set at maximum and minimum speeds,each of which remains practically constant for about 30% of thetotaltime of each work period; or a total of approximately 60% of constantspeed operation, and of varying speed operation,

durling each periodic and recurrent Work cyc e. i

The foregoing constitutes a description of a convenient and simple buteffective embodiment of the. means which I have invented for generatinga plurality of alternating electric currents o periodically varyingfrequency, and in -Which the maximum frequency of one current occurs "ata different time instant from that of the other, and

which are to be employed to operate intermittingly 'and alternately aplurality of groups of electric motors at varying speeds,

- each of which groups may @comprise a singhe 1motor, or a plurality ofmotors in para e Modifications of the construction and arrangementdescribed will occur to those skilled in the art to which the presentinvention relates. but it is to be understood that changes within thescope of the appended claims may be made without departing from thespirit of my invention.

Having thus described my invention, what I claim and desire to securebyLet-ters Patent of the United States, is:

1. In a varying frequency generating set, a plurality of alternatingcurrent generators, and means for driving the said generators at speedswhich periodically rise and i fall in the alternately recurring periods,

such means including a plurality of speedreducing gear trains, whosehigh speed ends ducing gear trains, whose high speed'ends are connectedto said generators, and noncircular ge'ars'connecting the lowspeed endsof'said speed-reducing trains.

3. In a varying frequency generating set, a plurality of alternatingcurrent generators, and means for driving the said generators, incombination with a plurality of speed-reducing gear trains each composedof circular gears, the high speed ends of the trains connected to thegenerators, and the low speed ends interconnected by means ofnon-circular gears.

a 4. In a varying frequency generating set, a plurality of alternatingcurrent generators, means for driving the same, and other means forcontrolling the said generators at speeds which periodically rise andfall in such manner that their instants'of maximum speed alternate inthe recurring periods,'said other means comprising a plurality ofspeed-reducing gear trains inter-connecting the said generators.

J 5. Two alternating .current generators with means for, driving thesame, a speedreducin'g gear train connected to each generator, and a setof irregular or non-circular gears connecting the said gear trains. I

6. In a varying frequency generator set, a plurality ofalternatingcurrent generators and means for driving the same, speed-re ducing geartrains connecting the said gen-' erators, such" gear trains beinginter-connected at their low speed ends by irregular or non-circulargears, in combination with a plurality of varying speed direct currentmachines, one for each generator, to supplement the action of the saidgear trains, and

means for driving the said direct current machines as described.

7. In a varying frequency generator set, a plurality of alternatingcurrent generators, and means for driving the same, in combination witha plurality ofspeed-reducinggear trains connected at their high speedends to the generators and at their low speed and including in thecombination connections for transferring power from one end of thegenerator set to the other.

In a varying frequency generator set, two alternating currentgenerators, a double rotation motor for driving such generators atvarying speeds which periodically rise and fall in alternately recurringperiods, and including 1n the combination means be-,

tween the generators for transferring power from one end of the set tothe vother, such means comprising inter-connected gearing.

10. In a varying frequency generator set, two alternating currentgenerators, a double 15 rotation motor for driving such generators atvarying speeds which periodically rise and fall in alternately recurringperiods, and including in the combination connections for transferringpower from one end of the generator set to the other to equalize thetorques exerted by the rotating elements of the motor.

In testimony whereof, I have signed my this 11th day-of No name atMilwaukee, vember, 1919.

JAS. ADAMS, JR.

Witnesses:

W. F. WOOLARD, 0.:THEO. OSTERBERG.

